The present invention generally relates to mobile station registration within a wireless communication network, and particularly relates to handoff procedures involving base stations that support concurrent services, e.g., voice and packet data services.
Wireless communication services continuously evolve, offering wireless service users an increasingly sophisticated range of services. One of the more useful innovations involves offering users the ability to engage in concurrent services, wherein a given user has two or more concurrent connections with the wireless network. For example, the wireless network provides the user's wireless communication device, e.g., mobile station, with concurrent voice and packet data connections allowing the user to carry on a voice conversation while browsing the Web or sending and receiving email. In some instances, the user may have multiple, concurrent data connections, with or without concurrent voice service. The evolving third generation (3G) wireless networks being developed under the cdma2000 family of standards, including those based on IS-2000 and 1xEV-DV standards, stand as examples of such concurrent service networks.
As with any increase in sophistication, the push toward concurrent services capability is not without its complications. Mobility management represents an ongoing challenge. For example, in a 1xEV-DV network, mobility management involves voice and data perspectives. Packet data traffic generally is routed between mobile stations and external public data networks (e.g., the Internet) using packet data serving nodes (PDSNs) coupled to a gateway router connected to the Internet. The PDSNs in turn route data to packet control functions (PCFs), which serve one or more base stations and act as a link between the packet network and the radio network.
In contrast, legacy “voice” services (i.e., circuit-switched voice and data) are routed from the mobile stations to legacy networks such as the Public Switched Telephone Network (PSTN) through mobile switching centers (MSCs) communicatively coupled to the supporting base stations. Thus, different network entities are involved in call support depending upon whether circuit-switched or packet-switched services are active. In concurrent service environments, both voice and packet data services may be active, which requires managing mobile station mobility from the perspective of both call types.
Mobile stations within the service area of a given base station typically monitor one or more overhead channels, such as paging or broadcast channels, used by the base stations to transmit information to the mobile station, for the needed identification parameters. The base station uses such channels to transmit various information to the mobile stations, including network identification parameters, which indicate to the mobile stations their service location within the network. For example, in a 1xEV-DV network, base stations (BSs) transmit network identification (NID), system identification (SID), and packet zone identification (PZID) values.
NIDs generally are used to divide a given geographic area into one or more service areas, and multiple NIDs typically are associated with a given base station. SIDs generally are defined at the MSC level, such that one MSC and all its associated base stations (e.g., a network “system”) share a unique SID. Note that NIDs may be reused from system-to-system, but SIDs are unique such that network systems are individually identifiable. PZIDs identify packet data coverage areas, which may differ from NID/SID coverage areas, since different network entities provide voice and packet services.
When a mobile station is idle, it generally recognizes its movement within a system by the changing NID values it receives, and recognizes its movement across systems by the changing SID values it receives. Similarly, changing PZIDs indicate movement across packet zone boundaries (e.g., movement across PCF coverage areas).
On the data side of the network, as the mobile station moves across a packet zone boundary, it establishes a new connection between the PCF controlling the new packet zone and the corresponding PDSN. If this corresponding PDSN is the same as the PDSN prior to the mobile station traversing the packet zone boundary, the PDSN tears down the connection to the previous PCF. If, however, the new packet zone corresponds to a different PDSN, then the new PDSN initiates new Point-to-Point Protocol (PPP) establishment procedures between the mobile station and itself, and performs mobile IP registration. In this way, as the mobile station moves, the connection to the PDSN is used to route the data to the appropriate PCF in whose coverage area the MS currently resides. The process of updating the new connection to the PDSN and any associated mobile Internet Protocol (IP) signaling may be regarded as the MS performing a “packet data registration” on the packet-switched side of the network.
On the voice side of the network, the mobile station re-registers with the network 10 as it moves through the different service areas such that location information in the mobile station's associated home location register (HLR) is updated to reflect its current service location. Such re-registration is important because the network uses the location information in the HLR to route mobile-terminated voice calls intended for the mobile station, i.e., incoming calls, to the appropriate network system. Thus, mobile station re-registration serves to update the HLR so that mobile-terminated calls are properly routed to the network entities in whose coverage area the mobile station currently resides.
An idle mobile station monitors one or more overhead channels, such as broadcast or paging channels transmitted by the base stations, for the needed identification parameters. Thus, an idle mobile station recognizes movement by receiving changed identification information on a monitored overhead channel. Such recognition generally triggers re-registration by the mobile station so that HLR information remains current. However, mobile stations generally do not monitor these overhead channels when they are engaged in active voice calls. Moreover, base stations generally are not aware of whether a given mobile station undergoing an active voice call handoff has an associated dormant packet data connection.
Because base stations generally cannot determine whether a dormant packet data session exists for a mobile station undergoing hard handoff during an active voice call, the base stations by default assume that such a connection might exist. Therefore, such base stations perform operations as part of handoff, or immediately subsequent to the handoff, to ensure that the mobile station receives updated network identification parameters such that the mobile station can re-activate any concurrent but dormant packet data session it might have. Such identification information typically is sent by the base station that received the mobile station in handoff using a channel associated with the voice call, such as a traffic channel.
Thus, the base station conveys identification parameters to the mobile station, including a current PZID, as part of receiving that mobile station in handoff. For example, in the cdma2000 family of standards, an In-System Traffic Parameters (ISTP) message is sent by dim-and-burst or blank-and-burst signaling on the voice traffic channel, or sent on an associated dedicated control channel, depending on the particular radio configuration being used. Regardless, providing the PZID value to the mobile station as part of voice call handoff procedures insures that the mobile station can determine if, as a consequence of the handoff, it has traversed any packet zone boundaries. Receipt of the PZID ensures that the mobile station can properly re-activate any dormant packet data session it might have subsequent to the handoff, and permits updating the connection to the PDSN. As noted earlier, proper packet data routing between the network and the mobile station depends on the mobile station having knowledge of the correct PZID.
In general, however, a mobile station undergoing voice call hard handoff between base stations supporting concurrent services receives updated NID, SID, and PZID values for the target (receiving) base station as part of the handoff procedure. Thus, when the mobile station is handed off from a source base station to the target base station while engaged in an active voice call, it typically receives updated NID, SID, and PZID values from the target base station as part of the ISTP message.
The mobile station updates its stored NID, SID, and PZID parameters based on the values received in the ISTP message, which action can delay re-registration of the mobile station at the conclusion of the voice call. For example, after termination of the active voice call, the mobile station again begins monitoring one or more overhead channels for identification parameter information. If the mobile station has remained in the service area of the target base station, its stored parameters will match those it obtains on the overhead channel.
Because of the matching NID/SID information, the mobile station does not recognize that it has moved from source base station to target base station and therefore does not re-register with the network. Where the movement was inter-system (i.e., between MSCs), this failure to re-register leaves the HLR with inaccurate location information for the mobile station. Such inaccurate information interferes with the network's ability to direct mobile-terminated voice calls to the mobile station. That is, by not re-registering, the HLR information for the mobile is not updated and subsequent mobile-terminated calls will not be properly routed, or at least will not be efficiently routed.